The thing to keep in mind is “locally measured.” As measured by a particular observer,c and phi have their invariant values wherever he or she is located. But everywhere else, thevalues measured may be quite different from the local invariant values.

where Woodward states that the speed of light is only invariant to a local observer but "everywhere else, the values measured may be quite different from the local invariant values" as we have been arguing this before with Mulletron, regarding the speed of light in a dielectric (or water, for that matter) as compared to the speed of light in vacuum. I understand Mulletron's argument that between the particles in any media there is a vacuum, but to make calculations one has to resort to field equations, (as done by Woodward) and then it is more expedient to adopt this viewpoint.

However, for Woodward's formulation in particular this fine point becomes all the finer, as the Woodward Mach Effect depends on these derivatives !

Hence, there is an insufficiently unexplored (from a theoretical and experimental viewpoint) problem here: as Woodward is using relativity field equations involving (time and space) derivatives in materials: I think its validity really, really requires experimental verification. Particularly when the Abraham/Minkowski paradox is unresolved.

Others may disagree with Woodward using relativity field equations for this, but I think he is (at least) consistent in this particular issue ( I have not explored the other 99%) .

However, nothing that I read (at least over the pages I looked at) feels like this site's subject matter, so I'm locking it (but putting it back on view) and we'll start a new thread in an attempt to make it relevant to this site. That's the best solution, better than leaving this in moderation.